Your question does not offer a lot of facts so any answer given will simply be based upon an overview of the law. I would highly recommend you seek out an experienced domestic relations lawyer who has a proven track record of success in custody cases and spend an hour going over your legal rights. I would also network with people you know who have hired someone in your area and been awarded custody by order of the court.
In response to your question generally, the court must make a decision regarding custody determining what is in the best interest of the child. As a result, the court must hear the evidence to determine which parent (if either) is most likely to be able to provide for the future care and upbringing of the child. Often times an expert (a psychologist, social worker or psychiatrist) will be hired to perform diagnostic tests regarding you, your spouse and the child.
The age of the child is also a factor in Ohio and a child does have the legal right to express an opinion (this right vests as early as age 7 but obviously the older and more mature a child is, the more likely his or her wishes will be considered).
Custody in Ohio is statutorily based so if you have internet access I would suggest you look at Ohio Revised Code Section 3109.04.
Unfortunately, without more information it is difficult to be more specific in a response.
Go find a qualified family lawyer and invest a few dollars in a consultation to see what your rights and chances are of success.